Diminished scale

The diminished scale, also known as the whole half scale, is an eight note scale with a numeric formula of 1-2-♭3-4-♭5-♯5-6-7-8/1. It is a symmetrical scale in that it follows a distinct pattern of steps, those being whole step, half step in a repeating pattern, not to be confused with the dominant diminished scale which follows a half step, whole step pattern. There are really only two distinct diminished scale patterns along with a third that covers most of the neck, this is due to the symmetry of the scale pattern. The first pattern has a sixth string tonic and the second has a fifth string tonic, the third pattern is an alternate that has an upward movement and has tonics on the fifth and sixth strings although in different keys.

As the diminished scale contains eight notes, we have to repeat one degree when writing the numeric or notated formula to complete the scale, there are many ways of doing this, and no single way is either write nor wrong. For the numeric formula I have repeated the fifth degree (one flat and one sharp) but you could also repeat the sixth degree, or double flat the seventh followed by a major seventh, or even make use of a flattened eighth.

The diminished scale can be written in three keys (E♭, D and D♭) which will cover every other key. For instance: A diminished is the same as E♭ diminished started on the fifth scale degree, and this is the same for F♯/G♭ and C diminished scales started on the third and seventh scale degrees respectively. Another way to look at it is to start from root position and move up in minor thirds which will produce the same result.

Harmonized diminished scale

Tertian harmony is the harmonization of a scale moving up in thirds, whether that be major or minor. Secundal harmony is the harmonization of a scale moving up in seconds and Quartal harmony is moving up in fourths. Using strict Tertian harmony principals when harmonizing the diminished scale (in other words using every second note in the scale for example: C-E-G) produces seven diminished triads and seven diminished seventh tetrads (aka: full diminished with a double flat seventh). Relaxing the rules and making use of Secundal and Quartal harmony opens up a plethora of chords as you are repeatedly given a choice of minor and major thirds, perfect fifths and flat fifths, and minor seventh degrees which is why one can harmonize such a large array of chords from one scale. There are no-less than twenty triads and twenty-five tetrads that can be built from the diminished scale and below I have written them down for all three keys (E♭, D and D♭). Take note of enharmonic notes and chords (example: C♯ is enharmonic to D♭ etc). If all you want is to view and learn the diminished scale patterns then just skip over this harmony section to the scale patterns below.